Rifle Scopes Optimized height and lenght on mount for AR15 style of rifles.

[Spuhr]

Hi

currently our cantilever mounts are 1,46" and 1,5" high.
For a number of users they are on the short side.
So I am scetching a new more extension mount.

Any input from you on what is the optimized AR height and how much more to extent the mount?
I am planning an extra 1" to 1,25" extension.

Håkan

 

[BobinNC]

Hakan,

Total Extension should be between a min of 1.77" (45mm) and a Max of 2.52" (64mm)

Ring Height: 1.575" (40mm) from top of 1913 rail to center of scope, this will clear most folding BUIS (Back Up Iron Sights) common on AR's

What you did not ask:

For AR use: Eliminate the bottom bubble level. On an AR running a BUIS you can't see it to use it anyway. If you want to provide a bubble level for AR users put it as an option on top of the rings (ala Nightforce) where it can be seen.

 

[Spuhr]

Thanks a lot.

There is a number who have asked for a lower mount so they can get a better cheekweld............
So again, seems like we are getting to a situation where not everybody will get happy (yes as usual)

Håkan

 

[BobinNC]

Thanks a lot.

There is a number who have asked for a lower mount so they can get a better cheekweld............
So again, seems like we are getting to a situation where not everybody will get happy (yes as usual)

Håkan

Haken,

You make a good point. For AR use maybe two heights would do it: 1.575" (40mm) for BUIS use and a lower height like 1.378" (35mm) for those that never want to run a BUIS.

Of course if you get too low they will never clear the front rail when they try to run a scope with a 50mm Objective or bigger which need rings at a minimum of 1.15" (29mm) in height just to get a hair clearance.

 

[Kiba]

Håkan, I have 3 of your cantilevers on ARs and here is my experience...

While I run PRS stocks on my precision ARs and thus don't have cheekweld issues with the current 1.46" height I'd prefer to see the AR cantilever mounts about 1.38" high. That's plenty for a 56mm scope + flip cap to clear a tubular free float handguard (without a rail installed on top of the handguard.) However, 1.38" may be too low for those using flipup/backup rear sights with optics with large eyepiece diameters.

Regarding the cantilever length, I find the current cantilever design plenty long for AR10 style rifles with longer upper receivers and rails but I feel the cantilever could be a little longer for AR15 style rifles with their shorter uppers & rails-- especially when using longer scopes. I have an S&B 5-25 on a JP SCR11 (standard AR15 style upper/rail/handguard) and even with the cantilever all the way forward on the rail on the receiver I had to lengthen the LOP on the PRS stock by about 0.7" to achieve good eye relief. The scope was just too close to my eye at my usual/preferred LOP and I couldn't install the cantilever any further forward so the only option was to increase the length of the stock.

While Bob mentioned doing away with the level I'd prefer it stay. On both of my precision ARs I don't run backup iron sights and can see/use the levels just fine.

 

[kombayotch]

I've been using your cantilever for 2 years now. I love how solid it is, and how streamlined it is. I really don't like things sticking out of my firearms that can snag on stuff, if they aren't needed.

I do find the height a bit high. I've played around with a cheap riser mount and rings, and find that a center scope height of 1.37-1.4" above the picatinni works the best. I don't get a good cheek weld with the 1.47" height shooting prone, but if I go lower than 1.37", it doesn't work well for standing position.

I agree about the bubble level. I can't focus on it unless I take my head off the stock, even with the way I have it mounted way forward. On my boltguns, I mount levels just rear of the front scope ring so that I just need to open my left eye to see them. These are sticking out the side too, so that is also helps. It isn't a feature that sold me on the mount. I bought your mount purely for it's rigidity. I have never used the accessory mounting features either. These and the level are just cost adders that I don't really need.

The bottom one is where I mount:

When I buy other company's cantilever mounts, I typically buy the 3" offset ones. These can be mounted further back to put scopes at the same distance as the 2" offset ones. They are much more flexible as a mounting option. None of them are as rigid as yours, and I only use them for close range applications.

 

[BERTMAN77MK2]

Awesome news! Glad to hear that one of the finest scope mounts made is gonna be available for AR's! Of course it is also great to see questions being asked before production. My only concern is +1 on the bubble level removal or move to a useable area.

 

[WaveNature]

I don't think this is what you're looking for but I couldn't help myself since no one makes a mount that fits me just right. I have a small face with high narrow cheek bones and a comparatively wide jaw so I doubt anyone will agree with this but here it is anyway:

My perfect mount would be 1.26-1.28 from top of the rail to center line of scope rings with a bare minimum of 2" forward extension (from the front face of the receiver to the rear face of the forward ring.)

If you make that in both 30 and 34mm, and 0 MOA and 20 MOA decline, I will be the first in line for three of them.



Also, I agree with kombayotch in that a more extended cantilever is more versatile than less extension, especially on AR15s.

 

[ptrlcop]

Maybe I am dense, but why would anyone run flip up irons with a non QD optic mount? If I were in a situation where I had the tools/opportunity to remove the optic and access the irons why would I not just repair/replace the optic?


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[MSTN]

Eugene Stoner designed the AR-15 with fixed carry handle to support the rear sight. When the gun evolved to its current flat top form, the axis of the carry handle mounted peep sight ended up 1.41" above the flat top of the upper receiver. So, that has become the benchmark for the axis height of both iron sights and magnified optics on the AR-15 platform. (NOT necessarily red dot sights).

Likewise, Eugene Stoner, while working for Reed Knight at the early Knight's Manufacturing Company, came up with 1.265" for the optimum scope axis height for the SR-25. Why lower than that of the AR-15? The bigger gun has more drop to the comb of the stock, due to the bulkier upper and lower receivers.

I think the man knew what he was doing.

The cheek weld is the same for both weapons. In other words, the distance from the top of the comb of the stock to the axis of the mounted optic (or rear peep sight) is the same.

To sacrifice the optimum cheek weld just to be able to stuff your favorite BUIS under the ocular lens of the scope is ludicrous.

 

[BobinNC]

Eugene Stoner designed the AR-15 with fixed carry handle to support the rear sight. When the gun evolved to its current flat top form, the axis of the carry handle mounted peep sight ended up 1.41" above the flat top of the upper receiver. So, that has become the benchmark for the axis height of both iron sights and magnified optics on the AR-15 platform. (NOT necessarily red dot sights).

Likewise, Eugene Stoner, while working for Reed Knight at the early Knight's Manufacturing Company, came up with 1.265" for the optimum scope axis height for the SR-25. Why lower than that of the AR-15? The bigger gun has more drop to the comb of the stock, due to the bulkier upper and lower receivers.

I think the man knew what he was doing.

The cheek weld is the same for both weapons. In other words, the distance from the top of the comb of the stock to the axis of the mounted optic (or rear peep sight) is the same.

To sacrifice the optimum cheek weld just to be able to stuff your favorite BUIS under the ocular lens of the scope is ludicrous.

Be sure to drop a note to the Crane Naval Warfare Center and tell them how ludicrous it is to build our troops MK12's Mod 1's with rings 1.45" high (ARMS #22 Highs) so they can clear the issued KAC Micro BUIS....That pesky 0.004" hundreds of an inch of extra height makes those rifles darn near useless...who knew?

 

[MSTN]

The MK 12 MOD 1 comes with the KAC 200-600 micrometer flip up rear sight, KAC P/N 98474, one of the lowest profile sights made when stowed, and clearance was never an issue. The Micros from KAC came several years later. The ARMS #22 high rings were all that were available at the time in commercial, off-the-shelf QD rings that were close to the right height. No, I wont quibble with you over 0.04" (not 0.004"). And yes, they're close enough for government work. Crappy product, ARMS #22 rings, in my experience, however. Much better choices are now available with appropriate forward offset for proper eye relief.

 

[redhooker]

Eugene Stoner designed the AR-15 with fixed carry handle to support the rear sight. When the gun evolved to its current flat top form, the axis of the carry handle mounted peep sight ended up 1.41" above the flat top of the upper receiver. So, that has become the benchmark for the axis height of both iron sights and magnified optics on the AR-15 platform. (NOT necessarily red dot sights).

Likewise, Eugene Stoner, while working for Reed Knight at the early Knight's Manufacturing Company, came up with 1.265" for the optimum scope axis height for the SR-25. Why lower than that of the AR-15? The bigger gun has more drop to the comb of the stock, due to the bulkier upper and lower receivers.

I think the man knew what he was doing.

The cheek weld is the same for both weapons. In other words, the distance from the top of the comb of the stock to the axis of the mounted optic (or rear peep sight) is the same.

To sacrifice the optimum cheek weld just to be able to stuff your favorite BUIS under the ocular lens of the scope is ludicrous.

That height with a 50 or 56mm bell in 20 moa will not clear a flat top rail, certainly not with any form of lens cap.

Hakan-how about a 30mm NON-cantalevered 1.35" 20 moa mount for the mono upper ARs. LMT and Colt to name 2 popular ones. Please.

 

[MSTN]

That height with a 50 or 56mm bell in 20 moa will not clear a flat top rail, certainly not with any form of lens cap.

Hakan-how about a 30mm NON-cantalevered 1.35" 20 moa mount for the mono upper ARs. LMT and Colt to name 2 popular ones. Please.

1.41" high Larue SPR-S mount with 10 MOA cant. Nightforce scope with 50 MM objective lens, 2.323" outside diameter (radius 1.161"). Even the bulky NF bikini lens cover can be installed. The NF 56MM objective has an outside diameter of 2.56" (radius 1.28"). So, you could use a Butler Creek cap or similar with a mount this height.

Spuhr already makes the mount you want, just 1.38" high:

SA-3601 - AI 30mm Dovetail Mount 6MIL/20.6MOA 1.38"

 

[MSTN]

Hi

currently our cantilever mounts are 1,46" and 1,5" high.
For a number of users they are on the short side.
So I am scetching a new more extension mount.

Any input from you on what is the optimized AR height and how much more to extent the mount?
I am planning an extra 1" to 1,25" extension.

Håkan

The height is driven by both optimum cheek weld and objective diameter requirements. So, you're in the ball park. Me, I like lower better than higher, especially prone. But, as the previous poster points out, you have to think about not only objective clearance but lens cap fit, too.

A 1.8" cantilever works well on the AR-15 family. None required on the big gas guns or monolithic designs.

 

[redhooker]

1.41" high Larue SPR-S mount with 10 MOA cant. Nightforce scope with 50 MM objective lens, 2.323" outside diameter (radius 1.161"). Even the bulky NF bikini lens cover can be installed. The NF 56MM objective has an outside diameter of 2.56" (radius 1.28"). So, you could use a Butler Creek cap or similar with a mount this height.

Spuhr already makes the mount you want, just 1.38" high:

SA-3601 - AI 30mm Dovetail Mount 6MIL/20.6MOA 1.38"

Won't work in a 20moa, the 1.125" unimount puts the bell solidly in the rail. The 1.375 high mount is about as low as you can go in a 20moa on a flattop, I currently also run a 1.45" high 20 moa mount also (I believe that is the height of the Spuhr cantilever mount) and a 56mm bell sits less than 1/4" off the rail.

Also you will have a tough time mounting that dovetail mount in the link above on your 1913 rail. Note the SA in the model number-that is for an AI chassis. You need and SP for picatinnay rail mounts. I have been through this before so I am not just speaking offhand, this is the voice of bitter experience.

 

[19Scout77]

Maybe I am dense, but why would anyone run flip up irons with a non QD optic mount? If I were in a situation where I had the tools/opportunity to remove the optic and access the irons why would I not just repair/replace the optic?


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How dare you interject logic into a discussion of accessories!! BTW, does this stock pack make my butt look big?

 

[E. Bryant]

The height is driven by both optimum cheek weld and objective diameter requirements.

The height is also driven by one of the original concerns of its designer, which was to keep muzzle rise to a minimum. Doing so required that the barrel be placed in line with the shooter's shoulder weld point, and that resulted in the nominal sight axis to barrel axis offset. Whether that remains an issue for precision shooting is another matter altogether, as recoil management techniques during semi-auto shooting do not necessitate such mechanical measures. Those shooting events requiring rapid placement of aimed fire from unsupported positions, such as three-gun, may still wish to utilize the concept to decrease the amount of muzzle displacement during recoil, and furthermore may want to tune that parameter to fit their particular shooting style and physical build.

 

[MSTN]

Also you will have a tough time mounting that dovetail mount in the link above on your 1913 rail. Note the SA in the model number-that is for an AI chassis. You need and SP for picatinnay rail mounts. I have been through this before so I am not just speaking offhand, this is the voice of bitter experience.

Noted and thanks for the heads up.

 

[Spuhr]

But we make a SP-3006 that is 30mm, straight and 1,35" high.
But without tilt.
We have not had sufficent interest to make that mount in a tilted version.
When it comes to Nightforce scopes, I really belive that you can live without tilt as they have so much elevation built in.

On my own "homebuild" Ar10 I am using 1,18" high mounts.
And I am pretty satisfied that I made the action 1,25" longer than a normal AR10 action (longer pic rail) othervise the eyerelief would have been impossible..........

Håkan

 

[Soct]

How dare you interject logic into a discussion of accessories!! BTW, does this stock pack make my butt look big?

No, it has flattering lines.

 

[redhooker]

But we make a SP-3006 that is 30mm, straight and 1,35" high.
But without tilt.
We have not had sufficent interest to make that mount in a tilted version.
When it comes to Nightforce scopes, I really belive that you can live without tilt as they have so much elevation built in.

On my own "homebuild" Ar10 I am using 1,18" high mounts.
And I am pretty satisfied that I made the action 1,25" longer than a normal AR10 action (longer pic rail) othervise the eyerelief would have been impossible..........

Håkan

i agree the NF does not need the cant, but I prefer it as it keeps the scope near the center of elevation travel throughout most distances I get to shoot (mostly under 900 yards). But if there was no interest ADM would not be selling a ton of these in 20moa:

American Defense MFG, LLC | Browse | Scope Mounts | AD-RECON-S Scope Mount

It would be nice to have other options as this is one of the only mounts in this style for us 30mm poor boys. There are at least 6 or 7 guys at my local range running this exact mount. Just sayin...

 

[Spuhr]

We have over 50 mount models in production and already that is a lot.
But we start up new models if there is a sufficient demand (20-30 ea on order from a distributor is sufficient ).

When looking at the chart you linked to I CSN see that their 30mm is 1,47" high.
We have 1,5" with 20 moa.

We also have 1.18" with 20 moa and as that works fine on My AR10 its possible it works on yours as well?

Håkan